For operational safety and accuracy, there is a need to keep the brain in wakefulness, for which people usually drink coffee or smoke cigarettes to keep the brain awake, and some people stimulate their head or body with mechanical or electrical means. The present invention provides a method of neural physiological stimulation to modulate neuronal activations in the brain for keeping the brain in wakefulness, including modulating upwards the neuronal activation at the brain site, locus coeruleus, via trigeminal nerve stimulation, as well as a neural physiological method of sensing the drowsiness of the brain for automatic control of the neural physiological stimulation for keeping the brain in wakefulness.